The damage caused by Hurricane Sandy will ultimately cost billions of dollars to repair, which has researchers wondering what the global cost of climate change could be. With so many of the world’s megacities at or below sea level, rising oceans and stronger storms present significant risks, not only to people living in these areas, but also to business activity. By some estimates, 9 percent of the world’s GDP will be taken up by the effects of climate change on just 10 of these coastal megacities by the middle of the century.

Conservative estimates place rising sea levels at 18 inches by 2070, while others expect an even higher rise once the melting Greenland and Arctic Ice sheets are factored in, resulting in an increase of 3 to 6 feet. As cities such as Calcutta, Shanghai, Mumbai and Bangkok continue to see explosive growth, the rising sea levels and increasingly intense storms pose an even greater risk. Combined with existing at-risk cities like New Orleans, New York, Tokyo and Amsterdam, the result is a costly and dangerous situation that could result in massive damage and loss of life worldwide.

Many established cities like Amsterdam and London have floodgates and levees in place to protect against flooding and once-in-a-lifetime storms. But many growing cities have little or no protection at all. Some of these cities are important industrial centers, producing goods for the planet that may be at risk. The floods in Bangkok, which disrupted computer and automobile manufacturing, made this particularly evident last year.

While there aren’t any easy solutions to the problem, what is evident is the fact that costly, significant steps will be increasingly necessary in order to protect the people and infrastructure of cities along the coasts. With estimated $35 trillion dollars at stake by 2070, it is clear that we simply can’t afford to wait.